About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

Quantum Cascade devices with an emission wavelength centered around 5 μm have been shaped into compact, yet long (8 mm and 12 mm) spiral cavities to increase mid-infrared superluminescence (SL) power. Up to ~57 mW of SL power at 250 K is obtained with a Gaussian emission spectrum with a full width at half maximum of 56 cm−1 and a coherence length of ~107 μm.

Figures (5)

(a) Optical microscope images of two spiral cavities with a total length of 8 mm (top) and 12 mm (bottom). (b) A schematic of the definition of positive and negative angles with respect to the 17° tilted front facet. (c) Far-field measurements taken at 80 K of the 8 mm device (blue) and the 12 mm device (red), both taken at ~2.6 A peak pulsed current.

Peak power vs. current taken under pulsed operation (100 ns pulse width at 5 kHz) across different temperatures for the 8 mm device (left, circles) and the 12 mm device (right, squares). The “X” marks the laser threshold. Close (open) symbols indicate the power below (above) threshold.

Superluminescence power taken at ~20 mA below the laser threshold vs. temperature. Blue circles and red squares correspond to the 8 mm and 12 mm device, respectively. The dashed lines are a guide to the eye.

(a) ASE spectra with a resolution of 0.125 cm−1 obtained in the fast scan mode of the FTIR of the 8 mm (blue) and 12 mm (red) devices at ~20 mA below threshold at 80 K. The black line corresponds to a Gaussian fit to the spectra. (b) The interferograms taken in step scan mode with a resolution of 16 cm−1 under the same operating conditions as the spectra shown in (a) of the 8 mm (blue) and 12 mm (red) devices. (c) ASE spectra taken under the same operating conditions and resolution as (a) at 250 K. The noisier spectrum in (c) would indicate that there is less power at 250 K, but the LI measurements indicate otherwise. (d) The interferograms taken under the same operating conditions and resolution as (b) at 250 K.) The offset in the Gaussian fit of (a) and (c) is due to the thermal background.